Automatic flow control mechanism for hydraulic power circuit



De 16, 1952 J. w. BRrDwELL ETAL 2,621,478

AUTOMATIC FLOW CONTROL MECHNISM FOR HYDRAULIC POWER CIRCUIT Filed March 28, 1949 5 Sheets-Sheet l @y k INVENToRs.

ATTORNEY Dec. 16, 1952 J, w BYRlDwELL ETAL 2,621,478

AUTOMATIC FLOW CONTROL MIEICHANISM FOR HYDRAULIC POWER CIRCUIT s sheets-'sheet 2 Filed March 28, 1949 m lllE my We mn/OMU A /0 wa Dec. 16, 1952 .1.w. BRlDwl-:LL ETAL 2,621,478

AUTOMATIC FLOW CONTROL MECHANISM FOR HYDRAULIC POWER CIRCUIT Filed March 28, 1949 5 Sheets-Sheet 4 IN V EN TORS.

ATTORN De@ 16 1952 1w. BRIDWELL ET AL 2,621,478

AUTOMATIC FLOW CONTROL MECHANISM FOR HYDRAULIC POWER CIRCUIT Filed March 2 8, 1949 5 Sheets-Sheet 5 'El Ef7 INVENTORY.

APatented Dec. 16, 1952 AUTOMATIC FLOW CONTROL MECHANISM l FOR HYDRAULIC POWER CIRCUIT John W. Bridwell and Morton M. Coker, Peoria, Ill., assignors to Caterpillar Tractor Co., Peoria, Ill., accrporation of California Application March 28, 1949, Serial No. 83,966

1 Claim.

This invention relatesy to a hydraulic control mechanism for directing iiuid under pressure to one or more double acting hydraulically actuated jacks.

The present invention is particularly adapted for use in connection with hydraulically actuated jacks for controlling the movement of an earth' working implement such as a tractor mounted bulldozer or the like and will be disclosed herein in connection with such use; Its adaptability to other uses will, however, be readily apparent.

A hydraulic circuit for controlling the movement of a tractor m-ounted bulldozer or thelike usually comprises one or more double acting hydraulically actuated jacks, a fluid reservoir, a pump, and a control valve for controlling the flow ofv'fiuid to and from the jacks.' The control valve is usually provided with four operating positions, namely, neutral or hold, raise, lower, and a so-called lioat positionin which the working implement is free to move in response to external forces. One of the principal difficulties encountered in conventionalv hydraulic systems of this type is that under certain operating conditions, the load on the working implement causes it to move faster than the rate at which the pump'can sup-ply fluid to the jacks. As a result, the fluid displaced from the jacks is returned to the supply tank at a higher rate than it is withdrawn by the pump thusvcausing excessive presf sures which may result in damage in the hydraulic system, as for instance, bursting of the fluid supply tank. 'A

It is one of the objects of this invention to provide an improved control valve for a 4hydraulic circuit having means to prevent fluid displaced from the jacks from returning to the supply tank at a greater rate than fluid is being withdrawn therefrom. It is another object of this invention to provide an improved manual control mechanism for a four position hydraulic control valve which includes means to permit the operator to identify the operating position of the valve by its feel, and means for returning the valve to its neutral position except when it is in the oat position; Further objects and advantages of this invention'will be apparent from the following description wherein reference is -made .to the accompanying drawings.`

In the drawings: y

Fig. -l is a vertical longitudinal sectional view througha control -valveembodying the present invention; f i Fig. 2 is a horizontal longitudinal sectional view` of the control valve shown in Fig. l, illustrating schematically its connection with a double acting hydraulic j-ack for controlling the movement of a bulldozer blade; y

Fig. 3 is a fragmentary sectional View similar to Fig.1 illustrating the valve spool in its position to effect lowering of the bulldozer;

Fig. 4 is a similar view illustrating the valve spool in its position to raise the bulldozer Fig. 5 is a similar view illustrating the'valve spool in its oat position; i.

Fig. 6 is a fragmentary sectional viewA similar to Fig. 2 illustrating the valve spoolfand its control linkage in the float position; Y

Fig. 7 is a longitudinal sectional View through a modified form of the control valve illustrated in FigsJl through 6; and

Fig. 8 is a longitudinal sectional view similar to Fig. '7 illustrating the valve spool in its raised position. v

.'Figs. 1 and 2Y of the drawings illustrate a hydraulic circuitl comprising a fluid supply tank I0, a pumpv I I, and acontrol valve I2 for directing fluid under pressure through power lines I3 and I4 to` either end of a double acting Ahydraulic jack, illustrated schematically in Fig.'2 ascomprising a cylinder I5 containing a reciprocal piston rod I6. The cylinder may be pivotally supported from a tractor or. the like (not shown) while' the -piston rod is pivotally secured to a bulldozer blade`I1.x The bulldozer blade is provided with a pair of push arms I8 which at their opposite ends are pivotally secured to the tractor in a manner to permit raising or lowering of the bulldozer in response to movement of the.' piston rod I6. The control valve I2 comprises a valve body I9 having an elongated bore 20 for the reception of a valve spool 2I adapted for sliding movement therein. The valve spool is .provided with aplurality of spaced collars 22, 23, 24, V25,

. 26, 21, and 28, which upon sliding movement of the valve spool Vare adapted to cooperate with spaced recesses 30, 3|, 32, 33, 34, 35, 36, and 3l to elfect direction of fluid from the pump through the control valve in a manner presently to be complished by means of a manually controlled linkage comprising a link 38, pivotally connected to the valve spool and at its opposite end` to a l lever 39 clamped against rotation on a shaft 40 extending through and rotatably supported in a Wall of the supply tank I0. At its extending end, the shaft 4|) may be connected to anysuitable manually; controlled linkage (not shown)` to effect sliding offthe valve spool in its bore upon rocking movement of the shaft 40. The

3 valve spool 2| is normally urged toward its neutral or hold position as illustrated in Figs. 1 and 2 by a spring 42 embracing the opposite end of the valve spool and interposed between a pair of thrust washers 43 and 44. The washer 43 is engageable by collar 28 and the end of the valve body.l I9.- while. the washer 44 engages a collar 45 adjacent the. end of the: valve spool anda shoulder 46 formed at the end of a cover 41 enclosing the mechanism which is secured to the valve body as by cap screw 43. The maximum axial displacement of the. valve. spool is.v limited by a sleeve 49 embracing the spring 42' and interposed between the.. washers. 43- and. 44.

Upon movement of the valvespool; to itsil'oatA position as is illustrated in Figs. and 6, itis.

held against the force of the springk 42 urging it toward the neutral position by a roller 56 carried in an arm 5I extending from the leven 39 which is adapted to engage a detent 52 provided in one endof a` bell-crank 53. The belle crank. ispivotally supportedfrom the valve-body and is normally held. in the position illustrated by.A means of a springr 54 and; anut 55- carried ony a stud 5.6A extending; from the.. valveA body through an opening in the crank. Spring 54 urges the bell-crank toward; clockwise rotation as viewed inv Fig. 6, which rotation is limited byjthe nut` 55: The bell-crank is. provided with a ramp 51 adjacent the detent 52 for' engage,- ment by the roller as the valvespool is, moved toits-lowering position. Further movementv of the valve spool tothe left,y as viewed in Fig, 2', is opposed by the spring- 54.- which permits the operator to positively identifythe iloat. position by feel. Upon receptionvoff the.` roller50, in the detent. 52,v the valve. spool'f is held inV the; float position-by the detent.

Figs. l and 2 illustrate the valve spoolin its neutral or hold position in, which fluid` under pressure from the' pump is. directedA throughI a fluid; inlet-passage 58.-torthe-recesses.3il,.32 and 3.6;- in. the bore Recesses: 3l andz36' are, in direct communication. with recesses;.3. and 31 respectively' which in:- turnz. are. open.. tok a. mani-,-

foldi 8l: thru which. all of; theuid from. the

pump. is returned to.. the. supply tank I0., The manifold is: of' relatively. large cross-sectional area and is. provided with apairy of spaced out:- lets-.821. and'. 83 to reducezthe velocity. andi con.- trol; the .directionA of. the returning' fluid thus minimizing turbulence aeration. of: thel fluid in.thertank. In thisv position, uidinpowerlines It andf I4 is prevented from. returning to. the tankby the collars:251andf' 26 respectively.

To lower the bulldozer: blade. the valve-spool sage`= 59 with-` an` elongatedbore- 69 which in turnV communicateswitht recess 31; by way of avv passage 6I. is returnedto thelsupply tank through the -manifold-T 8 I.

- InA order to prevent the'uiddisplaced from thejack returning tothe supply tankat a ratev greater thanthat at which fluid isV` withdrawn Fromthe'rrecess 31, the-displaced fluidn and directed to its opposite end by the pump, a counterbalance valve 62 is disposed for sliding movement in the bore 60. The counterbalance valve 62 is provided with spaced collars 63 and 64 for controlling the ow of displaced iluid through the bore and is normally urgedv towardv itsolosed position,v illustrated in Fig. l, by meanslof a.` spring 65'; interposed between the collar 64 and the adjacent end of the bore. In its closed position, the collar 64 prevents communication between the bore 60 and recess 31. Thecounterbalance valve is adapted to be moved to its open position as illustrated in Fig. 3 by luidpressurein either power line receiving pump output which istransmitted to the end of the borez lillA adjacent the collar 63 through a pipe 66. lnitsopenposition, the displaced iluid flows through spaced metering notches 61 provided in collar' 64=4 into recess 31 and thence to the supply tank. Thus, the displaced fluid from the jack is free. to return to thev supply tank only when there is'suflicient pressure in one of the power lines acting on the. collar 63 to4 compress the spring 65.

Referring now to Fig. 2, at itsopposite end theY pipe 66 communicatesY withI an elongated bore 68 which also communicates with the-bore 2|)A containing the valve spool 2'I, recess 33 communicatingA with power line I3, and recess 35 communicatingv withr power. line I4- by way4 of passages 69, 10,- and 1I, respectively. A shuttle valve'12` is disposedfor sliding movement in the bore 68 and is provided with spaced collars-13, 14, 1.5 and 16 which, upon sliding movement of the valve,I permit communication between the pipe- 66: and either passage- 10 or passage 1I. The shuttle valve is normally held inthe position. illustrated in Fig. 2- by a spring 11- interposed' between the collar 16'and the-end of the bore-68. In this pcsitiomthepipe 66 isin communication'withpassage 1I= which in turn communicates with the recess 3.5, thus fluid pressurein. power line I4A maybe-transmitted` to-the bore 66, moving the counterbalance valveV to Yits open-.position as described inthe following paragraph- Toy raise.; the, bulldozer blade',A the valve spool is movedto thee rightT toy thee position. illustrated in Fig; 4. Inthis positiomnuidis prevented from returningA to thesupply` tank through recesses 30 and-,31 by collars 23 andY 26 respectively, and the entire output of the pump is directed through recess 32, recess 33, and power line I3- to: the lowen endv of. the jack cylinder I5` retractingthe pistoniV rod IBLr In this position, power line-preslsure in theY bore 2llbetweencollars 24fandf25 is transmitted throughY passage- 69` (Fig,v 2) movingI the: shuttle valve to the right, providing;

communication between passage 10 andpipe 66: Fluid ,pressure in. recess. 33e is-v thenl transmitted through.. pipev 6.6.h moving: the counter-balance valve-62E toit'sppen: position. permittingthe huid displaced: from: the upper: end: of" the jack to; re.- turn tothe supply'tanic'. by. way.y of power. line I4; recessr35f, recessv 34a bore.Y 69;.recess231 andimanifoldl- BI.

Fig: 5J illustrates thevalve spool moved'. to its position to permit floating`l` of.' the'l bulldozer blade. In this position, the-'entirefoutput of the pump is returned to the supply tank byfwayof recesses 30 and 31 and as recesses 33 and35eare-opento each other,v fluidv is freeto ow back and forth between opposite ends of the jack in response to raising andloweringmovements ofthe-bulldozer'blade.. Because ofz, the volume occupied by the piston rod I8, movement of the bulldozer blade upwardly displaces a greater quantity of uid from the upper end of the cylinder than can be received in its lower end. The resultant pressure in the bore between the collars 25 and 21 actuates the shuttle valve 12 to theright as viewed in Fig. 2 permitting pressure in recess 33 to be transmitted through passage 10' and pipe 66, movingthe counterbalance valve 62 to its open position permitting the excess fluid from the upper end of the cylinder to be returned to the supply tank through the bore 60. In a like manner, movement of the bulldozer blade downwardly displaces a smaller volume of fluid from the lower end of the cylinder than is required yto ll its upper end. This movement results ina lower pressure in the bore 20 between the collarsr and 21 `than is pres-ent in the supply tank. Under this condition, make-up fluid is withdrawn from the supply tank through a pipe 18 (Fig. 1) which communicates with the bore 60 containing the counter-balance valve. The pipe 18 is normally closed by a spring-loaded check valve 19, which is adapted to be opened by the pressure differential between the bore 20 and the supply tank. The pressure in the bore 20 is communicated to the back of the valve 19 or to its spring chamber through thevv small bleed passage shown at 83 terminating ink an orifice 8|. s

The maximum pressurein the powerlines is limited by a spring-loaded relief valve 85 disposed within a passage 86 providing communication between the bore 63 containing the counter-balance valve and recess 3i] which is open to the supply tank. Passage 86 also communicates with a bore 61 providing communication between recesses and 3|. Communication between recesses 30 and 3| is normally prevented by means of a dump valve 88 which is urged toward the closed position illustrated in Fig. l by means of a spring 89 and power line pressure in the passagev86. In the event that pressure in either of the power lines exceeds a predetermined value, the relief valve 85 is opened, permitting fluid in the passage 86 to be discharged into the recess 30. Upon opening of the relief valve, the pressure in the bore 81 is reduced by virtue of a restricting orifice 90 interposed in the passage 86 between the relief 'valve and the bore 60. When the pressure in bore 81 is reduced, the dump valve 88 is moved to its open position by pump pressure present in recess 3| thus permitting direct communication between recess 3| and recess 30 which is open to the supply tank.

The dump valve 88 also serves to relieve excessive pump pressure occurring in the recess 3| due to a blocked condition occurring when the valve spool is moved from its neutral position to either raise or lower the bulldozer. This pressure is the result of spacing callars 23 through 21 from each other so that during movement of the valve spool in either direction away from neutral, it passes through a position wherein the power lines and return passages are prevented from communicating with each other and also with the pump. This spacing of the collars is provided to preclude the possibility of either of the power lines being open to a discharge passage before full pump pressure is directed through one of the power lines as might otherwise occur clue to manufacturing tolerances. For example, during movement of the valve spool from the neutral position illustrated in Fig. 1

to"th'e"raiseposition illustrated in Fig. 4 directing uid from the pump through power line I3, if. the collar 25 opened recess 33 to the bore 20 before the collar 26 closed the recess 3E to-recess 31 and collar 23 closed the recess 3| to recess 30, it would'bepossible for fluid in powerfline |3 to returndirectly to the tank by way of recesses 30 and 31. Under this condition, the bulldozer would be lowered by its own weight instead of raised and if the valve spool were maintained in this position for any length,l of time,v damage tothe tank might occur.

Figs.,7 and 8 illustratea modification. of the control valve illustrated in Figs. 1 through .6, in which like parts are identified by the same reference characters primed. In this modied form, the' valve body |9 is provided with an elongated bore 20 for the sliding reception of a valve spool 2|. The lvalve spool is provided with spaced collars 9|, 92, 93, 94, 95, 96, 91, 98, and 99, which upon sliding movement of the valve spool are adapted to cooperate with recesses lill, |02, |03, |94, |05, |06, and |01 provided in the bore 20' to effect direction of uid under pressure from the pump through the control valve in a man,- ner to 1 b e described. In this modification, vthe maximum pressure in the hydraulic system -is limited by a relief -,valve indicated at |00 associated with the pump V'I'he construction and operation ofthis relief valveare conventional and need not be illustrated.

The lprincipal difference between the control valve |2- and the control valve |2 illustrated in Figs.1 through 6 is that the return of fluid displaced from the jacks to the supply tank is controlled byv a pair of check valves I|| and ||2 disposed for sliding movement in spaced counterbores i9 and H provided in the Valve spool 2|. Counterbore ||3 communicates with the bore 20.' by way of ports- I6 provided in the valvespool between collars 9| and 9.2 and through ports ||1 between collars 92 and 93. Counterbore IM communicates with bore 20 through ports 8 provided'in' the valve spool between collars 91 and 98. and ports |19 between collars 98 and 99. Each of thev check -valvesis provided with a pair of spaced collars |20 and I 2|, which uponsliding movement of rthe check valve, are adapted'to control the ow of displaced fluid through their respective counterbores; Each of the check valves is `normally urged toward the closed position as is illustrated in Fig. 7 by means of a spring |22 interposed between the collar |20 and the end of the counterbores. The check valve is adapted to be moved to its open position by fluid pressure transmitted through a passage |23 in the valve spool providing communication between the end of the counterbore 3 adjacent the collar |2| and the bore 20 adjacent the periphery of the collar y97. The check valve ||2 is adapted to be moved to its open position by iiuid pressure transmitted through a passage |24 in the valve spool providing communication between the end of the counterbore ||4 adjacent collar |2| and the bore 20 adjacent the periphery of the collar 93.

Fig. '7 illustrates the valve spool in its neutral or hold position. At this time, all of the uid from the pump Il enters recesses |03 and |05 which are open to recess |04. The recess |04 communicates with a passage |25 providing communication between recesses ||l| and |01 and which also is open to the supply tank by way of a passage |26. In this position, uid in the power line I3' and I4 is prevented from returnlng`l`v to; the.y supply' tanks. by the. collars 92;, 93; and.' 911 Fig.. 8f illustrates. therein; speel ix:v positionzto effect. raisingl of' the. bulldozer. In. this posit-ioni the iiuid` in recesses |03 and |05 is prevented from returning to. the tank through recess. lili.Y

byf'the: cellarsv 94 and. 95.".` and pressure s from. the pampa is` directed through. metering noteliesil |21 provided;4 in` the collarI 9.1.' te; recess Ius.. Prem they recess. |06; the fluid isidirected tothe :leiter endforf-the jackl througnz pewer une? la". Fluid pressure in recess |86 isi-transmitted threughftlie passagev |23; moving the eheek valvel t'o its openpositien as illustrated; Whichzperinits the uldl displaced. from: the 'upper endify the jack tdreturntethe tankrbyway of pewer line- |43 recess |02. port. IIJ; eeunterbore |13; port. lilii recess: mi, passage |25", and passage |26.

Thefbuildozer may be lowered by.` ineving the valve spool toward the left as viewed 'in Fig;4 'I untilltherecess |03Ais/open t0 recess leomiunieating pressure fromthe puni'pthrough limiter ing notches |18 provided` in collar 93 reeese |n2, andi newerA line In* to thel 'upper endf efthe jack.

transmittedetlirughwthe passage l2'4,-,mving tll check-.valve |122 to its open pesitionprniittlig the-.- displacediluid from'k the jack. to return` .te theatanr by wayl ofv power line i3?, 'recess miti counter-bore H4; recess migranti passage 12:52

The oat position. may lie obtained' by :nuwee ment' of the valve'spoolifurther to the' left from the lbwering'positoriV until the cellar 94 prevents commumeation'between recesses `2 and 03- and the collar 91. prevents communication between recesses |052 and IUS; In this positioni the entire output'. of the. pump isy returned te the tank througlrrecess |041 and passage |26'i At tliis time;` recesses lezend: |1361V are open torecesses |91' and; HiT' respectively, which in turn are in diectacommunication. by-Y way of" the ypassage |25 permitting/freenet: of fluid` toveitlier` end of.' the jack. `Tine-difference in the quantity of. fluid displaced: from vopposite ends of trieV javali during' floating due .tothe volume occupied-by the piston redi'is eitherA addecler discharged through the' portilzs; v

. The modification f thev control valve illustrated: in Figs. '1.' a-nrlrS isl particularlyadapted foruse in: hydraulie-systems having;A a 'relativelyi small. capacity; Its. use' in: cjiirietier hydraiili systems; of relativelyA large capeity. is. also` possible. but mayy ina some cases prmie undesirable.becausefffthe necessity of-:a rather: large: Halve spool: to aeeoinmodate. c'cfuntertores ofsueienh size tuv secei'nirmdatey the: required' iduw.

In vhydraulc ereuitzolnprsin'g a.. fluid subie ply tank, a. pumpfffersupplying, uid under pressure. to.: a. pair: ef newer lines. each: of. which. eemmunieates; with eine) end; ef a double'. actingliyd'rauli jack, afceltrlf valve for contrellin the, new.4 ef; fluid: te. and from the; jack', andi means: for preventingtheY return. of' fluid. Adis' placed; frein.. the. jack. tea the:v supplyv tank' at a greater. rate than' fluidi being` directed-ta the opposite endY eff thel jaen. comprising' a fluid: re tul' lassaige; a ltrfbalan'e valve- 'normally closingsaid passageand' adapted te be opened' by: mudpressure iii the power 'line direet'iiie mild fni` tlef iii tthe jaek', means fer automatically 'lieti. tl passage Cea'tar'iing the Vmunter-iiali-meevalve only with the 'ppwer line-'directing duidrrem: thepump te the jaar;

seid@ lest means including' a shuttle valve-riorfinallyV providing eommu'nication betweenV the passage containing' thel counterebalence valve and elle of the fawe'i lis r'idladapted t6 be mevd t-'a @edition ylerevi'diig commuiiicatln between said passage and the opposite' @einer linelby-fluidpressure in seid eppesite-iiewei 'line wherrlt is receiving fluidi frln the pil-imi.

f JOHN W; BRIDWELL.

MGRTG-N- COKER.

REFERENCES CITED.Y y The"iellmvine;referenmas are ffrecord in the iile efthispatent':

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